Combination starter-generator

ABSTRACT

A combination starter-generator system for use in a vehicle is provided. The vehicle has an internal combustion engine and a battery. The system includes a starter-generator electrically coupled to the battery to generate a current and to start the internal combustion engine. A drive mechanism connects the starter-generator machine and the internal combustion engine. The starter-generator machine generates the current by receiving a charging torque from one side of the drive mechanism and starts the internal combustion engine by imparting a starting torque to a different side of the drive mechanism. The charging torque or the starting torque is a greater torque. A passive tensioning system cooperates with the drive mechanism to tension the drive mechanism only at the side of the greater torque.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 09/865,210, filed May 24, 2001. This application also claimsthe benefit of U.S. Provisional Patent Application No. 60/273,191 filedon Mar. 2, 2001 and bearing Attorney Docket No. DP-302111, the contentsof which are incorporated herein.

TECHNICAL FIELD

This application relates generally to vehicles having a combinationstarter-generator. More specifically, this application relates totensioning systems and drives for combination starter-generators.

BACKGROUND

Prior internal combustion engine includes both a starter machine and agenerator or alternator machine (hereinafter generator). The starterprovides an engine-cranking torque to the flywheel or crankshaft of theengine in order to rotate the camshaft and facilitate the movement ofthe pistons during the ignition of the engine. The generator provides anelectrical output in order to meet the electrical loads of the vehicle,as well as to charge the vehicle's battery. Generally, a torque isapplied to a pulley of the generator by a belt frictionally engaged witha pulley of the generator and a pulley of the engine in order togenerate the electrical charge from the generator.

The concept of using only one machine to do both functions, namelystarting and generating, adds efficiency. Thus, starter-generators useless space, weigh less, eliminate the cost of one of the machines andreduce assembly time. However, starter-generators give rise to issuesdescribed below that affect the cost, complexity, and reliability ofsuch starter-generator systems. Accordingly, there is a continuing needfor inexpensive, reliable tensioning systems for starter-generators.

SUMMARY

A combination starter-generator system for use in a vehicle having aninternal combustion engine is provided. A drive mechanism connects thestarter-generator machine and the internal combustion engine. Thestarter-generator machine generates a current by receiving a chargingtorque from one side of the drive mechanism and starts the internalcombustion engine by imparting a starting torque to a different side ofthe drive mechanism. Depending on the application, the charging torqueor the starting torque is a greater torque. A passive tensioning systemcooperates with the drive mechanism to tension the drive mechanism onlyat the side of the greater torque.

An apparatus for starting an internal combustion engine having astarter-generator machine is provided. The starter-generator machine isoperable in a first direction for generating a current and a seconddirection for starting the internal combustion engine. A drive mechanismconnects the starter-generator machine and the internal combustionengine by a non-adjusting gear ratio in a range between 2:1 to 3:1. Thestarter-generator machine operates in the first direction to generate acurrent by receiving a charging torque from the internal combustionengine imparted to a first side of the drive mechanism. Thestarter-generator machine operates in the second direction to start theinternal combustion engine by imparting a starting torque to a secondside of the drive mechanism. A first tensioning system cooperates withthe drive mechanism to tension the drive mechanism at the first sideduring application of the charging torque. A second tensioning systemcooperates with the drive mechanism to tension the drive mechanism atthe second side during application of the starting torque.

An active tensioning system for use on a drive mechanism is provided.The drive mechanism creates a first slack side and a first tight side ofthe drive mechanism. The drive mechanism also creates a second slackside and a second slack side of the drive mechanism. The first slackside and the second tight side are coincident. Similarly, the secondslack side and the first tight side are coincident. The activetensioning system has a guide. A first idler sprocket is operativelycoupled with the first slack side of the drive mechanism and is slidableon the guide. A second idler sprocket is operatively coupled with thesecond slack side of the drive mechanism and is also slidable on theguide. A spring connects the first idler sprocket and the second idlersprocket. The spring also biases the first idler sprocket and the secondidler sprocket towards one another such that upon creation of the firstslack side and the first tight side, the first tight side acts upon thesecond idler sprocket to slide the first idler sprocket and the secondidler sprocket upon the guide to tension the drive mechanism, and suchthat upon creation of the second slack side and the second tight side,the second tight side acts upon the first idler sprocket to slide thefirst idler sprocket and the second idler sprocket upon the guide totension the drive mechanism.

A combination starter-generator system is provided. The vehicle has aninternal combustion engine and a starter-generator machine forgenerating a current and starting the internal combustion engine. Adrive mechanism connects the starter-generator machine and the internalcombustion engine. The starter-generator machine charges the battery byreceiving a charging torque from a first side of the drive mechanism.The starter-generator machine starts the internal combustion engine byimparting a starting torque to a second side of the drive mechanism. Thedrive mechanism compensates for differences in the charging torque andthe starting torque with a non-adjusting gear ratio in a range between2:1 to 3:1. An active tensioning system cooperating with the drivemechanism to tension the drive mechanism at the first side duringapplication of the charging torque or at the second side duringapplication of the starting torque.

The above-described and other features and advantages of the presentinvention will be appreciated and understood by those skilled in the artfrom the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a belt or chain drive mechanism;

FIG. 2 is a block diagram of a starter-generator circuit;

FIG. 3 is a first step of a control sequence of the circuit of FIG. 2;

FIG. 4 is a second step of a control sequence of the circuit of FIG. 2;

FIG. 5 is a third step of a control sequence of the circuit of FIG. 2;

FIG. 6 is a fourth step of a control sequence of the circuit of FIG. 2;

FIG. 7 is a top view of a first embodiment of a starter-generatorsystem;

FIG. 8 is a front view of a first embodiment of a tensioning system forthe starter-generator system of FIG. 7;

FIG. 9 is a front view of second embodiment of a tensioning system forthe starter-generator system of FIG. 7;

FIG. 10 is a front view of third embodiment of a tensioning system forthe starter-generator system of FIG. 7;

FIG. 11 is a front view of fourth embodiment of a tensioning system forthe starter-generator system of FIG. 7;

FIG. 12 is a top view of a second embodiment of a starter-generatorsystem;

FIG. 13 is a view of a first embodiment of a tensioning system on thestarter-generator system of FIG. 12, taken along lines A-A;

FIG. 14 is a view of a second embodiment of a tensioning system on thestarter-generator system of FIG. 12, taken along lines A-A;

FIG. 15 is a top view of a third embodiment of a starter-generatorsystem; and

FIG. 16 is a view of a tensioning system for the starter-generatorsystem of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Starter-generators give rise to issues that affect the cost, complexity,and reliability of such systems. First, the drive mechanism connected toa starter-generator handles power in two directions, which presents aunique tensioning problem for the drive mechanism. Second, there is alarge gap between torque and speed requirements for starting an engineversus generating electricity. The differing torque and speedrequirements have typically been overcome by the use of transmissionhaving a different ratio for each the starting function and thegenerating function. Such transmissions typically required a gearbox anda switching clutch, which adds cost, complexity, and decreasedreliability of starter-generators.

Referring to the Figures and particularly to FIG. 1, a belt or chaindrive mechanism 10 is shown handling power transmission in twodirections, and, thus illustrates the unique tensioning problem for thedrive mechanism. Drive mechanism 10 includes a first pulley or sprocket12, a second pulley or sprocket 14 and a chain or belt 16. In theinstance where first sprocket 12 is the drive sprocket driving mechanism10 in the direction of arrow 18, second sprocket 14 becomes the drivensprocket and first sprocket 12 acts on chain 16 such that the chain hasa tight-side or pulled-side 20 and a slack-side or pushed side 22.

Conversely, in the instance where second sprocket 14 is the drivesprocket driving mechanism 10 in the direction of arrow 24, firstsprocket 12 becomes the driven sprocket and second sprocket 14 acts onchain 16 such that the chain has a tight-side 26 and a slack-side 28. Ineither instance, a chain tensioner is needed on slack-side 22 and 28 tomaintain chain 16 operatively engaged with drive sprocket 12 and 14,respectively. Thus, where the drive sprocket and the driven sprocketchange place, the tight-side and slack-side of drive mechanism 10 alsochange place, giving rise to a need for more than one tensioner in thedrive mechanism. It should be noted that the belt or chain of drivemechanism 10 does not change its direction of rotation, rather only thesource of power (i.e., the drive sprocket) changes.

Embodiments of starter-generator system 100 are illustrated in FIGS. 7,12 and 14. Generally, system 100 provides a starting function to aninternal combustion engine 110 and a generating function to a battery140. System 100 includes a starter-generator 130 electrically coupled tobattery 140 by a lead 141. Starter-generator 130 is operativelyconnected to engine 110 by a belt or chain drive mechanism 10. Thus,starter-generator 130 performs dual functions of starting engine 110 andgenerating electrical output to battery 140. Belt or chain drivemechanism 10 is described in this application by way of example aseither a belt drive mechanism or a chain drive mechanism, however bothbelt and chain drive mechanisms are considered within the scope of thepresent invention.

Starter-generator 130 is adapted to provide either an engine-crankingtorque 200 to drive mechanism 10 or receive a generator-cranking torque300 from the drive mechanism. By way of example, operation ofstarter-generator 130 is described with respect to FIGS. 2 through 6.Starter-generator 130 is a three-phase rotary machine including arectifier bridge 30 and a unit 32 for controlling the rectifier bridge.Starter-generator 130 includes a coil-carrying rotor 34 constituting theprimary magnetic circuit associated with two rings and with two brushesthat convey excitation current (of the order of a few amps); and astator 36 carrying a plurality of coils constituting the secondarymagnetic circuit, connected in star or delta configuration in the commoncase of a three-phase structure and acting, during generating operation,to deliver converted electrical power to the rectifier bridge 30(several tens of amps at a voltage of the same order as the batteryvoltage).

Bridge 30 is connected to the various phases of the stator 36 and isconnected between ground and a power supply terminal of a battery 140.Bridge 30 includes a plurality of diodes 40 forming a rectifier bridge,and a plurality of switches 42, such as transistors. Switches 42 areconnected in parallel with respective diodes 40 and control the variousphases (e.g., starting and generating) of starter-generator 130.

During a starting function, diodes 40 act as freewheel diodes, whereasin a generating function, the diodes act as a rectifier bridge. Switches42 are advantageously MOSFET type transistors. Switches 42 include adiode between drain and source. Consequently, the switches 42 enablebridge 30 to be implemented using transistor components only that thenact both as switches and as freewheel diodes.

The starting function of starter-generator 130 is achieved by imposingDC on the primary magnetic circuit rotor 34 and by delivering signalsthat are phase-shifted by 120 degrees to the phases of stator 36, whichsignals are ideally sinewave signals, but may optionally be squarewavesignals or trapezoidal wave signals. Referring now to FIGS. 3 through 6,an example of a control sequence for switches 42 is illustrated. Thesequence is made up of squarewave signals issued by the control unit.The signals A, B, and C shown in these Figures are control signals forthose of switches 42 in bridge 30 which are connected to ground. Thesignals A′, B′, and C′ which control the other transistors, i.e. thoseconnected to battery 140, are signals that are inverted relative to thesignals A, B, and C, without overlapping them. This is shown in FIG. 6where the signal C′ is drawn for controlling the transistor connected tothe transistor controlled by the signal C. With this kind of control,the rotor performs one full revolution while each of the phases goesthrough a number of periods equal to the number of pairs of poles of therotor (e.g. eight).

This starting operation is used for driving engine 110 to start it,thereby making it possible to eliminate the starter and the associateddrive ring, and also the power cabling generally associated with thestarter. To enable engine 110 to be started in this way, the controlsignals for switches 42 are advantageously variable frequency signals,at a frequency that is regulated to be increasing by unit 32, so as toavoid any slip of the rotor relative to the rotating magnetic fieldcreated by the stator. For example, frequency regulation may be providedby unit 32 in such a manner so as to guarantee that the alternator has aspeed profile enabling the engine to be started.

Control unit 32 includes a means for recognizing a code signal thatauthorizes engine starting. This signal is transmitted to the unit 32 bya code transmitter means inside the vehicle. The unit 32 switches on thetransistors 42 in a manner suitable for starting the engine only if itreceives the code signal. Consequently, the control unit 32 and the codetransmitter means which transmit the unlocking signal to said unit,constitute a system for immobilizing the engine.

After engine 110 has started, unit 32 controls the transistors 42 so asto operate in a generating mode. Unit 32 controls switches 42 so thatall of them are open circuit across the terminals of all of the diodes.The bridge 32 then reverts to being a rectifier bridge. In anotherpossible embodiment, the transistors 42 are controlled so as to shortcircuit the conductive diodes. They are caused to be open circuit onlyacross the terminals of non-conductive diodes. Thus, a current no longerpasses through the conductive diodes, such that the short circuits madein this way serve to reduce losses. To synchronize control oftransistors 42 relative to the switching from the conductive state tothe non-conductive state of diodes 40, unit 32 is connected to a meansfor detecting when diodes 40 pass from one state to another. By way ofexample, these means may be constituted by a sensor, such as a Halleffect sensor, for measuring the angular position of the rotor relativeto the stator. Such a sensor may also be used for determining the speedof the rotor, e.g. by counting pulses in a given time window, so as toenable the unit to detect that engine 110 has started and thus switchfrom operating in starting mode to operating in generating mode.

Also, means 44 are provided for regulating voltage so as to maintain thevoltage of battery 140 at a suitable level. Provision is also made for aswitch 46, e.g. another MOSFET type switch, whose ON or OFF state iscontrolled by the control unit. Switch 46 is designed to short circuitthe regulator in starting mode so that the secondary magnetic circuit 36is then directly excited by battery 140.

Thus when starter-generator 130 is in the starting mode, engine-crankingtorque 200 is applied by drive mechanism 10 from the starter-generatorto engine 110. Moreover, when starter-generator 130 is in the generatingmode, generator-cranking torque 300 is applied by drive mechanism 10from engine 110 to the starter-generator. It should be recognized thatthe operation of starter-generator 130 has been described above by wayof example only and that other starter-generators adapted to provide astarting function to engine 110 and a generating function to battery 140are considered within the scope of the present invention.

Starter-generator 130 described above is adapted for use in the positiontypically used for either automobile starters or alternators. Therefore,no complicated design changes to engine 110 are required forimplementation of starter-generator 130.

Referring now to FIG. 7, a tensioning system 100 is illustrated. System100 includes engine 110, a starter-generator 130 electrically coupled tobattery 140 by a lead 141 and belt or chain drive mechanism 10. Oncestarted, engine 110 drives a flywheel 116 operatively connected to atransmission 105 to propel the vehicle. Drive mechanism 10 has a singlebelt 150 connected to engine 110, and starter-generator 130.

Engine 110 includes a crankshaft 112 having a crank pulley 114operatively connected thereto. Similarly, starter-generator 130 includesa starter-generator shaft 132 having a starter-generator pulley 134operatively connected thereto. Belt 150 is configured to frictionallyengage pulleys 114 and 134. In addition, and if necessary, belt 150 isconfigured to drive pulleys of other vehicle accessory systems,including but not limited to cooling systems, air conditioning systemsand power steering systems. For example, a pulley 124 is illustrated asdriving a water pump 120 of an engine cooling system. Of course, othersystems may or may not be driven by belt 150. At a minimum, system 100includes belt 150 and pulleys 114 and 134. Thus, as crank pulley 14 isdriven by engine 110, belt 150 rotates pulleys 114 and 134.

Upon activation by a user, starter-generator 130 draws energy frombattery 140 through lead 141 to rotate starter-generator shaft 132.Shown in FIG. 8, starter-generator shaft 132 in turn rotatesstarter-generator pulley 134 to impart engine-cranking torque 200 tobelt 150. Thus, belt 150 being operatively connected to crank pulley 114drives crankshaft 112. Engine-cranking torque 200 acts on crankshaft 112to rotate engine 110 as required for engine starting procedures.

As shown in FIG. 8, during the starting of engine 110, belt 150 has atight-side 133 and a slack-side 135 created on either side ofstarter-generator pulley 134. A passive tensioning system 170 isprovided at slack-side 135 of belt 150 to remove the slack, keeping thebelt in operative engagement with starter-generator pulley 134. Passivetensioning system 170 includes an idler pulley 172 biased into operativeengagement with belt 150 so as to remove the slack from slack-side 135of the belt. Preferably, pulley 172 is biased into operative engagementwith belt 150 by a spring connection 174 mounted on engine 110 orelsewhere on the vehicle, such as, but not limited to the transmission,the exhaust manifold, or the vehicle body.

After engine 110 has been started, starter-generator 130 generates anelectrical output to battery 140 through lead 141. Shown in FIG. 9,engine 110 rotates crankshaft 112 and crankshaft pulley 114 to impart agenerator-cranking torque 300 to belt 150. Thus, belt 150 beingoperatively connected to starter-generator pulley 134 drivesstarter-generator shaft 132. Generator-cranking torque 300 acts onstarter-generator shaft 132 to rotate starter-generator 130, whichgenerates the electrical output to battery 140 through lead 141.Starter-generator 130 is described by way of example as receivingelectrical energy from and providing electrical energy to battery 140,however it is considered within the scope of the present invention forthe starter-generator to receive or provide electrical energy to or fromother devices. In one embodiment, generator-cranking torque 300 alsoacts to rotate pump pulley 124 of water pump 120 in order to provide aflow of cooling fluid to engine 110 as required in engine coolingsystems.

During the generation of the electrical output to battery bystarter-generator 130 shown in FIG. 9, belt 150 has a tight-side 113 anda slack-side 115 on either side of crankshaft pulley 114. Passivetensioning system 170 is also provided at slack-side 115 of belt 150 toremove the slack, keeping the belt in operative engagement withcrankshaft pulley 114. Idler pulley 172 is biased into operativeengagement with belt 150 so as to remove the slack from slack-side 115of belt 150. Preferably, pulley 172 is biased into operative engagementwith belt 150 by spring connection 174 mounted on engine 110 orelsewhere on the vehicle, such as, but not limited to the transmission,the exhaust manifold, or the vehicle body.

Accordingly, tensioning system 170 maintains belt 150 in engagement withpulleys 114 and 134 during the charging and starting operations,respectively. It has been determined that drive mechanism 10 havingtensioning system 170 only on the slack-side of the pulley 114 or 134generating the greater torque is sufficient for proper operation ofstarter-generator 130. More specifically, passive tensioning system 170is placed at slack side 115 when generator-cranking torque 300 isgreater than engine-cranking torque 200 as shown in FIG. 9. Alternately,passive tensioning system 170 is placed at slack-side 135 whenengine-cranking torque 200 is greater than generator-cranking torque300, as shown in FIG. 8.

For example, if engine-cranking torque 200 is greater thangenerator-cranking torque 300 (e.g., engine 110 is started at very coldambient temperatures when oil in the engine is very viscous), thentensioning system 170 is provided only at slack-side 135. Oppositely, ifengine-cranking torque 200 is lower than generator-cranking torque 300(e.g., high electrical load on battery 140), then tensioning system 170is provided only at slack-side 115. The life of belt 150 is typicallyinversely proportional to its maximum tension. Thus, placing passivetensioning system 170 only on one of slack-sides 115 and 135 increasesthe service life of belt 150.

An alternate embodiment of the tensioning system is illustrated in FIG.10. Here, component parts performing similar or analogous functions arenumbered in multiples of one hundred. In this embodiment, an activetensioning system 270 is provided for starter-generator pulley 134 andan active tensioning system 370 is provided for crank pulley 114. Activetensioning systems 270 and 370 actively or automatically engage drivemechanism 10 as needed. In this embodiment, active tensioning system 270includes an idler pulley 272, a spring connection 274, and a solenoid276. Spring connection 274 is mounted on engine 110 or elsewhere on thevehicle, such as, but not limited to the transmission, the exhaustmanifold, or the vehicle body. Solenoid 276 is adapted to extend idlerpulley 272 into operative engagement with slack-side 135, and springconnection 274 is adapted to retract the idler pulley upon deactivationof the solenoid. Similarly, active tensioning system 370 includes anidler pulley 372, a spring connection 374 and a solenoid 376. Springconnection 374 is mounted on engine 110 or elsewhere on the vehicle,such as, but not limited to the transmission, the exhaust manifold, orthe vehicle body. Solenoid 376 is adapted to extend idler pulley 372into operative engagement with slack-side 115, and spring connection 374is adapted to retract the idler pulley upon deactivation of thesolenoid.

Thus, during starting when engine-cranking torque 200 is imparted tobelt 150 to create slack-side 135 and tight-side 133 (shown in FIG. 10in dotted lines), solenoid 276 of active tensioning system 270 isactivated to extend idler pulley 272 into operative engagement with theslack-side. After engine 110 has been started and engine-cranking torque200 is removed from belt 150, solenoid 276 of active tensioning system270 is deactivated such that spring connection 274 retracts idler pulley272 out of operative engagement with slack-side 135.

Similarly, during generation of energy when generator-cranking torque300 is imparted to belt 150 to create slack-side 115 and tight-side 113(shown in FIG. 10 in solid lines), solenoid 376 of active tensioningsystem 370 is activated to extend idler pulley 372 into operativeengagement with the slack-side. After battery 140 has been charged andgenerator-cranking torque 300 is removed from belt 150, solenoid 376 ofactive tensioning system 370 is deactivated such that spring connection374 retracts idler pulley 372 out of operative engagement withslack-side 115.

The selective extension and retraction of active tensioning systems 270and 370 increases the service life in belt 150 since, as discussedabove, the life of the belt 150 is inversely proportional to its maximumtension.

Another embodiment of the tensioning system is provided in FIG. 11. Inthis embodiment, passive tensioning system 470 is provided for crankpulley 114 and active tensioning system 570 is provided forstarter-generator pulley 134. Active tensioning system 570 includes anidler pulley 572, a spring connection 574, and solenoid 576. Springconnection 574 is mounted on engine 110 or elsewhere on the vehicle,such as, but not limited to the transmission, the exhaust manifold, orthe vehicle body. Solenoid 576 is adapted to extend idler pulley 572into operative engagement with slack-side 135, and spring connection 574is adapted to retract the idler pulley upon deactivation of thesolenoid. Passive tensioning system 470 includes idler pulley 472 andspring connection 474 mounted on engine 110 or elsewhere on the vehicle,such as, but not limited to the transmission, the exhaust manifold, orthe vehicle body. Spring connection 474 biases idler pulley 472 intooperative engagement with slack-side 115. In this embodiment, springconnection 474 of passive tensioning system 470 biases idler pulley 472into operative engagement with slack side 115 regardless of the state ofgenerator-cranking torque 300.

Thus, during starting when engine-cranking torque 200 is imparted tobelt 150 to create slack-side 135 and tight-side 133 (shown in FIG. 11in dotted lines), solenoid 576 of active tensioning system 570 isactivated to extend idler pulley 572 into operative engagement with theslack-side. After engine 110 has been started and engine-cranking torque200 is removed from belt 150, solenoid 576 of active tensioning system570 is deactivated such that spring connection 574 retracts idler pulley572 out of operative engagement with slack-side 135.

The selective extension and retraction of tensioning system 570increases the service life in belt 150 since, as discussed above, thelife of the belt is typically inversely proportional to its maximumtension. The inclusion of one active tensioning system 570 and onepassive tensioning system 470 decreases complexity and cost. Activetensioning system 570 has a low power/energy requirement since solenoid576 is activated for only used for a very short time, namely duringengine cranking.

Active tensioning systems 270, 370, and 570 are described above by wayof example as including solenoids 276, 376, and 576 and springconnections 274, 374, and 574. However, alternate devices for extendingand retracting idler pulley 272, 372, and 574 are considered within thescope of the present invention. For example, alternate embodimentsinclude, but are not limited to, extension and retraction by anactuator, or a lever.

An alternate embodiment of starter-generator system 100 is illustratedin FIGS. 12 through 14. System 100 includes engine 110, astarter-generator 130 electrically coupled to battery 140 by a lead 141and belt or chain drive mechanism 10, namely a chain 160. Once started,engine 110 drives a flywheel 116 operatively connected to a transmission105 to propel the vehicle and drives a crankshaft 112 having a crankpulley 114 operatively connected thereto.

Cooling system 120 includes a pump-shaft 122 having a pump pulley 124operatively connected thereto and starter-generator 130 includes astarter-generator shaft 132 having a starter-generator sprocket 134operatively connected thereto. Accessory belt 150 operatively connectscrank pulley 114 and pump pulley 124. A chain 160 operatively connectsstarter-generator sprocket 134 and flywheel 116.

Upon activation by a user, starter-generator 130 draws energy frombattery 140 through lead 141 to rotate starter-generator shaft 132.Shown in FIG. 13 in dotted lines, starter-generator shaft 132 in turnrotates starter-generator sprocket 134 to impart an engine-crankingtorque 200 to chain 160. Thus, engine-cranking torque 200 acts onflywheel 116 to rotate engine 110 as required for engine startingprocedures. During the starting of engine 110, chain 160 has atight-side 133 and a slack-side 135 on either side of starter-generatorsprocket 134. A tensioning system 180 is provided at slack-side 135 ofchain 160 to remove the slack, keeping the chain in operative engagementwith starter-generator sprocket 134.

After engine 110 has been started, starter-generator 130 generates anelectrical output to battery 140 through lead 141. Engine 110, whenrunning, rotates flywheel 116 and crankshaft pulley 114. Belt 150 beingoperatively connected to crankshaft pulley 114 and cooling system pulley124, acts to rotate pump-shaft 122 to drive cooling system 120 in orderto provide cooling to engine 110. Simultaneously, flywheel 116 imparts agenerator-cranking torque 300 to chain 160.

Generator-cranking torque 300 acts on starter-generator shaft 132 torotate starter-generator 130, which generates the electrical output tobattery 140 through lead 141. During the generation of the electricaloutput to battery 140 by starter-generator 130, chain 160 has atight-side 117 and a slack-side 118 on either side of flywheel 116,shown in FIG. 13 in solid lines. Tensioning system 180 is also providedat slack-side 118 of chain 160 to remove the slack, keeping the chain inoperative engagement with flywheel 116.

Tensioning system 180 is an active tensioning system, namely it activelyor automatically tensions chain 160 as needed. Tensioning system 180includes a guide 182, a first idler sprocket 184, a second idlersprocket 186, and a spring 188. Guide 182, preferably a shaft, ismounted on engine 110 or elsewhere on the vehicle, such as, but notlimited to the transmission, the exhaust manifold, or the vehicle body.First idler sprocket 184 is adapted to slide or float up and down onguide 182. Similarly, second idler sprocket 186 is adapted to slide orfloat up and down on guide 182. First idler sprocket 184 and secondidler sprocket 186 are tied together by spring 188 such that the springbiases the sprockets 184, 186 towards one another. Thus, the assembly offirst idler sprocket 184, second idler sprocket 186, and spring 188 arepermitted to slide together on guide 182.

During starting, shown in FIG. 13 in dotted lines, the tension intight-side 133 of chain 160 acts on second idler sprocket 186 to slidetensioning system 180 downwards until first idler sprocket 184 takes upthe slack in slack-side 135. Thus, tensioning system 180 being in itslower position and being biased by spring 188 takes up the slack inchain 160. During generating, shown in solid lines, the tension intight-side 117 of chain 160 acts on first idler sprocket 184 to slidetensioning system 180 upwards until second idler sprocket 186 takes upthe slack in slack-side 135. Thus, tensioning system 180 being in itsupper position and being biased by spring 188 takes up the stack inchain 160.

Friction between guide 182 and sprockets 184, 186 acts to dampenvibrations induced by chain 160 traveling. Alternately, an active meansof damping (not shown) such as, but not limited to a hydraulic damperattached between guide 182 and sprockets 184, 186 and/or spring 188 isused to further dampen vibrations induced by traveling of chain 160.

Referring now to FIG. 14, a tensioning system 280 is illustrated. Duringthe generation of the electrical output to battery 140 bystarter-generator 130, chain 160 has a tight-side 117 and a slack-side118 on either side of flywheel 116. During starting, chain 160 has atight-side 133 and a slack-side 135 on either side of starter-generatorpulley 134.

Tensioning system 280 is a constant tensioning system, namely itprovides tension to chain 160 during starting, generating and staticconditions. Tensioning system 280 includes a first or upper tensioningmechanism 282 and a second or lower tensioning mechanism 284. Uppertensioning mechanism 282 biases a low-friction chain guide 286 intooperative engagement with chain 160 by a spring connection 288 mountedon engine 110 or elsewhere on the vehicle, such as, but not limited tothe transmission, the exhaust manifold, or the vehicle body.

Lower tensioning mechanism 284 includes an idler sprocket 290 inoperative engagement with chain 160. Sprocket 290 is rotatably mountedby a bracket 292 to engine 110 or elsewhere on the vehicle, such as, butnot limited to the transmission, the exhaust manifold, or the vehiclebody. Bracket 292 is adapted to mount idler sprocket 290 in operativeengagement with chain 160. For example, bracket 292 includes a take-upsystem, such as but not limited to a screw 294 and a slot 296.Accordingly, lower tensioning mechanism 284 removes any initial slackfrom belt 160 in a normal or static state.

During starting or the application of starting torque 200, springconnection 288 of upper tensioning mechanism 282 biases low-frictionchain guide 286 towards chain 160 to remove slack from slack-side 135.During generating or the application of generating torque 300, idlersprocket 290 continues to tension slack from slack-side 118 of chain160, while low-friction chain guide 286 of upper tensioning mechanism282 applies a very low drag force on the chain. Accordingly, duringgenerating upper tensioning mechanism 282 does not affect theperformance of chain drive mechanism 10 since the upper tensioningmechanism is not adding additional load to the chain.

Yet another embodiment of starter-generator system 100 is provided inFIGS. 15 and 16. System 100 includes engine 110, a starter-generator 130electrically coupled to battery 140 by a lead 141 and belt or chaindrive mechanism 10, namely a belt 190. Once started, engine 110 drives aflywheel 116 operatively connected to a transmission 105 to propel thevehicle. Engine 110 includes a crankshaft 112 having an accessory pulley108 and a crank pulley 114 operatively connected thereto.

Cooling system 120 includes a pump-shaft 122 having a pump pulley 124operatively connected thereto and starter-generator 130 includes astarter-generator shaft 132 having a starter-generator pulley 134operatively connected thereto. Accessory belt 150 operatively connectsaccessory pulley 108 and pump pulley 124. Belt 190 operatively connectsstarter-generator pulley 134 and crank pulley 114.

Upon activation by a user, starter-generator 130 draws energy frombattery 140 through lead 141 to rotate starter-generator shaft 132.Shown in FIG. 16 in dotted lines, starter-generator shaft 132 in turnrotates starter-generator pulley 134 to impart an engine-cranking torque200 to starter-generator belt 190. Thus, engine-cranking torque 200 actson crank pulley 114 to rotate engine 110 as required for engine startingprocedures. During the starting of engine 110, starter-generator belt190 has a tight-side 133 and a slack-side 135 on either side ofstarter-generator pulley 134. Tensioning system 180 is provided atslack-side 135 of belt 190 to remove the slack, keeping the belt inoperative engagement with starter-generator pulley 134.

After engine 110 has been started, starter-generator 130 generates anelectrical output to battery 140 through lead 141. Engine 110, whenrunning, rotates and crank pulley 114. Accessory belt 150 beingoperatively connected to accessory pulley 108 and cooling system pulley124, acts to rotate pump-shaft 122 to drive cooling system 120 in orderto provide cooling to engine 110. Simultaneously, crank pulley 114imparts a generator-cranking torque 300 to belt 190.

Generator-cranking torque 300 acts on starter-generator shaft 132 torotate starter-generator 130, which generates the electrical output tobattery 140 through lead 141. During the generation of the electricaloutput to battery 140 by starter-generator 130, belt 190 has atight-side 117 and a slack-side 118 on either side of crank pulley 114,as shown in FIG. 16 in solid lines. Tensioning system 180 is alsoprovided at slack-side 118 of belt 190 to remove the slack, keeping thebelt in operative engagement with crank pulley 114.

Tensioning system 180 shown in FIG. 16, similar to the discussion abovewith respect to FIG. 13, is an active tensioning system that actively orautomatically engages belt 190 as needed. Tensioning system 180 includesguide 182, first idler pulley 184, second idler pulley 186, and spring188. Guide 182, preferably a shaft, is mounted on engine 110 orelsewhere on the vehicle, such as, but not limited to the transmission,the exhaust manifold, or the vehicle body. First idler pulley 184 isadapted to slide or float up and down on guide 182. Similarly, secondidler pulley 186 is adapted to slide or float up and down on guide 182.First idler pulley 184 and second idler pulley 186 are tied together byspring 188 such that the spring biases the pulley 184, 186 towards oneanother. Thus, the assembly of first idler pulley 184, second idlerpulley 186, and spring 188 are permitted to slide together on guide 182.

During starting, shown in FIG. 16 in dotted lines, the tension intight-side 133 of belt 190 acts on second idler pulley 186 to slidetensioning system 180 downwards until first idler pulley 184 takes upthe slack in slack-side 135. Thus, tensioning system 180 being in itslower position and being biased by spring 188 takes up the slack in belt190. During generating, shown in solid lines, the tension in tight-side117 of belt 190 acts on first idler pulley 184 to slide tensioningsystem 180 upwards until second idler pulley 186 takes up the slack inslack-side 118. Thus, tensioning system 180 being in its upper positionand being biased by spring 188 takes up the slack in belt 190.

For purposes of clarity, tensioning system 180 has been described by wayof example as part of a two pulley/sprocket system. However, it isconsidered within the scope of the present invention for use of suchtensioning systems 180 with pulley/sprocket systems having more than twopulleys.

A difference between torque and speed requirements for starting anengine versus generating electricity exists. The tensioning systemsdescribed herein ensure that the belt/chain remains operativelyconnected to its respective pulleys/sprockets. Thus, it has beendetermined that the effect of the torque difference on starter-generator130 is minimized by adjusting the gear ratio of starter-generator pulley134 with respect to crank pulley 114 (or flywheel 116).

Engine-cranking torque 200, namely the torque supplied to crankshaft112, is equal to the torque provided by starter-generator 130 multipliedby the gear ratio of the starter-generator pulley 134 with respect tothe crank pulley 114. The gear ratio should desirably be between 2:1 and3:1. For example, if the gear ratio is 3:1 and engine 110 requires 150foot-pounds of torque for starting purposes, starter-generator 130 mustgenerate 50 foot-pounds (ignoring losses) to provide the required 150foot-pounds at crankshaft 112.

Additionally, the electrical energy generated by starter-generator 130is proportional to the speed of crankshaft 112. Thus, at highercrankshaft 112 speeds more electrical energy is generated, and,conversely, at lower crankshaft speeds less electrical energy isgenerated. Thus, in the example provided above where the gear ratio is3:1, if crankshaft 112 has a speed of 1000 rpm, starter-generator shaft132 has a resulting speed of 3000 rpm.

Setting the gear ratio at higher than the desired range of between 2:1and 3:1, would decrease the amount of torque starter-generator 130 mustgenerate to provide the required engine-cranking torque 200. Forexample, if the gear ratio is 10:1 and engine 110 requires 150foot-pounds of torque for starting purposes, starter-generator 130 mustgenerate only 15 foot-pounds (ignoring losses) to provide the required150 foot-pounds at crankshaft 112. Moreover, in this example, ifcrankshaft 112 has a speed of 1000 rpm, starter-generator shaft 132 hasa resulting speed of 10,000 rpm. Thus, when the ratio is set such thatstarter-generator 130 is required to produce low amounts of torque, theresulting speed of starter-generator shaft 132 tends to exceed themaximum rate determined from mechanical and/or electrical restrictionsin high velocity revolution. However, it has been found that the desiredratio of between 2:1 and 3:1 balances the speed of starter-generatorshaft 132 and the amount of torque starter-generator 130 must generate.

Thus, starter-generator system 100 provides a low cost method forachieving a starter-generator. Drive mechanism 10 includes simple activeand passive tensioning systems. Moreover, starter-generator system 100eliminates the need for gearboxes and their switching clutches tocompensate for torque and speed differences during starting andgenerating.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. An apparatus for starting an internal combustion engine, comprising:a starter-generator; a drive mechanism drivingly connecting a portion ofsaid starter-generator and a crankshaft of the internal combustionengine at a crankshaft pulley of the internal combustion engine; saiddrive mechanism being configured to transfer a first torque from saidportion to said crankshaft when the internal combustion engine is beingstarted such that said crankshaft is rotated by said starter-generator,said starter-generator facilitating the starting of the internalcombustion engine when said crankshaft is rotated; said drive mechanismbeing configured to transfer a second torque from said crankshaft tosaid portion when the internal combustion engine is running such thatsaid portion is rotated by said crankshaft, said starter-generatorgenerating an electrical current when said portion is rotated; a firstportion of said drive mechanism requiring tension during the transfer ofsaid first torque; a second portion of said drive mechanism requiringtension during the transfer of said second torque; and a tensioningmechanism configured to provide selectable active tension to said firstportion of said drive mechanism independent of a tension applied to saidsecond portion of said drive mechanism and also configured to provideselectable active tension to said second portion of said drive mechanismindependent of a tension applied to said first portion of said drivemechanism, said tension mechanism in operative engagement with only oneof said first portion and said second portion, said tensioning mechanismproviding tension to said drive mechanism at said first portion whensaid first torque is greater than said second torque, and saidtensioning mechanism providing tension to said drive mechanism at saidsecond portion when said second torque is greater than said firsttorque.
 2. (canceled)
 3. The apparatus as in claim 1, wherein said drivemechanism is a belt or a chain.
 4. The apparatus as in claim 3, whereinsaid tensioning mechanism comprises an idler pulley biased intooperative engagement with said drive mechanism.
 5. (canceled)
 6. Theapparatus as in claim 1, wherein said drive mechanism drivingly connectssaid portion of said starter-generator and said crankshaft of theinternal combustion engine with a non-adjusting gear ratio.
 7. Theapparatus as in claim 6, wherein said non-adjusting gear ratio is in arange between 2:1 and 3:1.